30 CFR § 23.11
How approvals are granted.
All approvals are granted by official letter from MSHA. A device will be
approved under this part only when the testing engineers have judged that it
has met the requirements of the part and MSHA's records are complete,
including drawings from the manufacturer that show the device as it is to be
commercially made. Individual parts of devices will not be approved. No
verbal reports of the investigation will be given and no informal approvals
will be granted. As soon as the manufacturer has received the formal
approval, he shall be free to advertise his device as permissible.
[Sched. 9B, 4 FR 1555, Apr. 11, 1939, as amended by Supp. 1, 20 FR 2975, May